By exploring the weldability of 316L austenitic stainless steel, an effective welding process was planned, including the following aspects: selection of welding rods and wires, corresponding welding process parameters, post-welding treatment, etc., which can effectively Improve welding quality.


1. Analysis of weldability of 316L stainless steel

(1)316L welding cracks. Generally speaking, the thermal conductivity parameters of 316L austenitic stainless steel are only half of those of low carbon steel, but the corresponding linear expansion coefficient is relatively large. It can be seen that there is a large welding stress at the hard joint position.

316L austenitic stainless steel has a large boundary between liquid and solid, and recrystallization takes a long time. Due to the strong dendrite directionality of austenite crystal, there is serious impurity segregation.

(2)316L austenitic stainless steel welding process. The following methods are generally used to weld 316L austenitic stainless steel: electrode arc welding, argon arc welding, gas welding, submerged arc automatic welding, etc. In order to ensure that the welded joints of 316L austenitic stainless steel can meet the performance requirements, the corresponding welding materials are generally selected according to the "composition" principle. At the same time, in order to improve the welding joint's resistance to welding hot cracks and corresponding intergranular corrosion, the welding wire position H00Cr19Ni2Mo2 is often used.

First, the carbon content of this welding material is relatively low, generally around 0.03%. Since C is the main element that causes inter-grade corrosion in steel, when the combined carbon content is below 0.03%, less carbon is precipitated, and when it is higher than this range, the amount of carbon precipitated will greatly increase. At the same time, carbon is It is more prominent in causing welding hot cracks. From this point of view, welding materials with a relatively high carbon content should be selected in this category.

Second, because the welding rod contains Nb element, it can react with carbon to form stable carbides, which can effectively avoid the phenomenon of chromium deficiency in austenite grain boundaries, thus improving the resistance to intergranular corrosion.

Third, the chromium content of this type of welding rod is generally about 85%. The chromium element can form corresponding ferrite in the weld, mainly because the diffusion rate of chromium element in austenite is lower than that of ferrite, so it can It can be seen that when chromium diffuses in ferrite, it can effectively reduce the chromium deficiency phenomenon at the austenite grain boundary, thereby effectively preventing intergranular corrosion. At the same time, the ferrite and corresponding austenite produced in the weld can effectively prevent welding hot cracks. If about 5% ferrite appears in the weld, it can effectively prevent the expansion of austenite grains, which will refine the grains and evenly disperse weld impurities. Fourth, this American welding rod is an alkaline low-hydrogen coating, which has high thermal crack resistance and can effectively prevent welding hot cracks.

(3) Welding process. 1) Preparation before welding. During the welding process, in order to effectively prevent carbon and impurities from entering the weld, it is generally necessary to use acetone to wipe the area between 2mm and 30m on both sides of the weld. At the same time, the oxide layer on the surface should be brushed off with stainless steel wire and wiped clean with acetone.


2. The following aspects need to be paid attention to in the welding process: First, since the most obvious characteristic of austenite is that it is very sensitive to overheating, the belt must be welded with a small current and a fast pressing method, and the corresponding welding current is generally average. Less than 20% of low carbon steel, this can effectively prevent intergranular corrosion and corresponding welding deformation. Second, in order to ensure stable arc combustion, argon arc welding mainly uses DC forward connection, while manual arc welding uses DC reverse connection. Third, when using argon arc welding for bottoming, the corresponding weld thickness should be as low as possible, so as to form a good fusion with the root. When closing the arc, a gentle slope should also be formed. For example: hand arc welding requires the use of a short Arc welding should be carried out slowly during arc closing, so that the arc crater can be filled and crater cracks can be prevented. Fourth, forced cooling should be performed after welding.


3. Post-weld treatment. During surface treatment, the following defects may appear on the surface of stainless steel weldments, such as scratches, dents, and rough spots, which will accelerate the corrosion rate of the weldment. Generally, the surface of stainless steel can be polished, which can effectively improve the corrosion resistance.